Power unit



Nov. 14,1939. BRUNNER 2,180,138

POWER UNIT Filed Feb. 5, 1937 Patented Nov. 14, 1939 UNITED STATES POWERUNIT Adolf Brunner, Winte'rthur, Switzerland, assignor to SulzerFriares, Socit, Anonyme, Winterthur, Switzerland Application February 5,1937, Serial No, 124,345

In Switzerland February 26, 1936 x This invention relates to internalcombustion engine-electric power units and particularly to units inwhich the engine drives a generator having field-regulating meansoperated by a servo- ,5 motor, whereby the generator is controlled tomaintain the engine torque constant.

In power units of this type, when the servomotor comprises adouble-acting piston and a valve whereby the supply of oil underpressure to 9,9 the servo-cylinder on opposite sides of the piston iscontrolled so as to move a field-regulating rheostat in one direction orthe other, failure of the supply of oil under pressure to theservo-piston may result in the rheostat stopping in a position ;15 whichwill result in the engine being overloaded.

With a view to improving reliability in operation, it has been proposedto supply pressure medium 'to the servo-cylinder only on one side of asingleacting piston for increasing the excitation current of the maingenerator, the return movement of the piston being efiected by springpressure. Such arrangements are, however, open to the disadvantage thatat starting of the engine the fieldregulating servo-motor sets theexcitation current at a minimum value so that acceleration of a vehicledriven by the power unit is liable to be delayed on, account ofinsuflicient excitation. This is more particularly the case when thegenerator is furnished with an unregulated shunt excitation p and aregulated separate excitation, since the servo-motor regulating theseparate excitation takes an appreciable time to reach the positioncorresponding to maximum excitation.

According to the present invention, means are 5 provided whereby, in theevent of the power supply for operating the field-regulating servomotorbecoming defective, the fuel supply to the engine is automaticallyreduced or cut off.

Preferably the arrangement is such that, when L4:0 the fuel supply isautomatically reduced or cut ofithe field-regulating servo-motor isautomatically adjusted towards a setting corresponding to maximumexcitation of the main generator, so that if the engine is automaticallystopped a ve 45 hicle driven by power derived from the power unit can berapidly accelerated when the engine is restarted.

In a preferred arrangement according to the invention an automaticcontrol device isprovided 50 which is normally held inoperative by powerderived from the source which supplies the power for actuating theservo-motor, and interconnecting means are provided between theautomatic control device and a fuel regulator for the engine 5 so thatthe event of the said power supply 7 Claims. (01. 290-17) failing theautomatic control device operates the fuel regulator to reduce or cutoff the *fuel supply.

Two constructiona each according to the invention,- are diagrammaticallyillustrated by Way oi example in Figures 1 and 2 respectively of the .5accompanying drawing.-

In the construction shown in Figure l, the engine l, which is of thefuel injection compression ignition typ e,'drives a main generator 2 andalso an auxiliary generator 3. The main 10 generator 2 supplies thecurrent for driving the motors l of a vehicle and is provided with ashunt field winding 5. The separate excitation machine 3 suppliescurrent to a separate field winding-6 the efiective value of which iscontrolled by a resistance I. The main generator 2 is also furnishedwith a counter-compound winding 8. i

. The engine crankshaft is coupled through gear wheels 9 to a camshaftl0 which not only drives a governor i I but also operates the plungersof a fuel injection pump l2. The sleeve B3 of the governor Hisengaged byone end of a lever l4 pivoted on afixed part at l5, the other end of thelever l4 cooperating with the spindle iii of a valve I! for controllingthe supply of pressure fluid, such for example as oil, from a mainsupply p pe. is to theoppositesides of a piston l9; arranged within afield-regulating servomotor, 25]. The piston i9 0:" the servo-motor isconnected, as shown, to a rheostat arm 2! which regulates the efiectivevalue of the resistance 1,- thus influencing the excitation of the maingenerator 2. The excitationof the generator 2 is thus automaticallyregulated so that the engine torque tends to be maintained constant forany given engine speed.

I In the arrangement, thus far described, should the piston Q9 of thefield regulating servo-motor 2d bein a position corresponding to a lowvalue 40 of, the resistance 1, that is to say a high excitation current,and the supply of pressure medium to the supply pipe it then fail orbecome defective, the engine may be seriously overloaded. With a view toovercoming this difiiculty an automatic control device is providedcomprising a piston 25, arranged withina cylinder 26 communicating withthe supply pipe it, the piston 25, which is upwardly biased by a spring21, cooperating with.

a stop 28 secured to the spindle it, the spring 2'! thus acting inopposition to the pressure of the medium supplied through the pipe 18.For the purpose of stopping the engine 1 at will, one end 29 of the fuelregulator 24 cooperates with a plunger or stop member 30 which can bemoved manually by a lever 3i (provided with a locking device not shown),the plunger 3!) being arranged in a cylinder 32 to which pressure mediumcan be supplied through a pipe 33 from a remote control to operate theplunger 39.

The lever I4 is yieldingly connected to the spindle 56 by a spring 35whose lower end bears against a collar 35 carried at the lower end ofthe spindle l6, while the upper end of this spring bears against acollar 3! carried by the lever I4, the spring 35 thus tending tomaintain the collar 37. in contact with a stop 38 carried by the spindleit. The spindle l6, and therefore the valve ll, can thus be moveddownwardly independently of the governor H, a suitable packing beingprovided between the spindle l6 and a sleeve 39 through which thespindle passes so as to prevent pressure medium from leaking throughthis joint.

With the parts in the positions shown in Figure l, the governor 'l I isin its position of equilibrium since the excitation of the generator 2has been set by the fie d-regulating servo-motor 20 in such a manner asto correspond to the engine torque which is to be maintained constant atthe desired engine speed and to the quantity of fuel supplied as set bythe regulator 24. The valve I7 is now also in its position ofequilibrium, that is to say the central position in which it preventseither the supply of pressure medium to, or discharge of pressure mediumfrom, the cylinder 20. The pressure medium in the pipe 18 now maintainsthe piston 25 in its lowermost or inoperative posi- I tion, that is tosay with the lower end of the pistcn 25 in contact with the base of thecylinder 26, the spring 2? being compressed and the spindle it togetherwith its stop 23 is free to be moved vertically by the lever l4.

In the event or" the supply of pressure medium to the pipe 13 failing,the spring 21 will move the piston 25 into the position so that the stop28 is engaged by the piston 25 and the spindle I6 is moved upwardly.Since the spring 27! is stronger than the spring 35, the latter will becompressed owing to the position of the lever I4 remaining unaltered.The upward movement of the spindle l6, however, causes the bell-cranklever 22 to be turned in the clockwise direction as viewed in thedrawing, so that the fuel regulator 24 is moved to the left. If thesupply pressure in the pipe [8 wholfy falls the bell-crank lever 22 willbe moved into the position shown at O and the engine Will be stopped.When the engine has come to rest, the governor sleeve [3 is moved intothe position X but, since the spring 35 will be thus compressed, thebell-crank lever 22 will remain in the upward position 0.

After the irregularity which has caused the defect in the supply ofpressure medium to the pipe [8 has been rectified,,the fuel regulator 24is set in an intermediate position, that is to say between the positionsand X, suitable for restarting the engine, by turning the lever 22manually or by transmission mechanism (not shown) in theccunter-cockwise direction. This rotation of the bell-crank lever causesthe spindle IE to be moved downwardly so that the stop 28 pulls thepiston 25 downwardly and compresses the spring 25. When the pressure inthe pipe I8 is restored, the piston is again held in the lowermostposition shown in the drawing.

When it desired to stop the engine independently cf the automaticcontrol apparatus the lever 33 is moved, either manually or by thepneumatic remote control means, from the position X to the position 0 sothat the plunger 36 engages the end 29 of the fuel regulator 24 andmoves this to the left whereby the bell-crank lever 22 is turned in theclockwise direction into the position 0. Since the valve ii isyieldingly coupled to the lever l4, operation of the fuel regulator 24by means of the lever St to stop the engine also lifts the valve ll intothe position so that pressure medium is supplied to the cylinder 2%above the piston is and the rhecstat arm 2! is moved downwardly so as todecrease the effective value of the resistance 7 to the minimum. Thus,when the engine is stopped, the field-regulating servomotor isautomatically set to correspond to maximum excitation of the maingenerator 2. When therefore the engine is to be restarted, the bellcranklever 22 is again turned in the counterclockwise direction into thehalf-load position as above indicated, so that the control valve I! ismoved downwardly but not sufiiciently to allow discharge of pressuremedium from the cylinder 20 above the piston I9.

It will therefore be seen that the servo-motor 20 is automatically setfor maximum excitation of the generator 2 not only when the supply ofpressure medium has failed and the engine automatically stopped, butalso when the engine is stopped by means of the lever 3|, so that whenthe engine is restarted and a switch 48 for the separate excitation 6 isclosed, maximum excitation of the generator 2 will be availableimmediately, thereby providing rapid acceleration with consequent savingof time.

In the arrangement illustrated in Figure 2, the automatic control deviceitself constitutes a servo-motor comprising a piston 46 arranged in acylinder 4 I, this arrangement allowing the governor II to be madesmaller and more'sensitive since the power for controlling the fuelregulator and field-regulating servo-motor is supplied by the pressuremedium through the pipe IS.

The sleeve iii of the governor H is connected to one end of a lever 62which is pivotally connected at an intermediate point to a piston valve43 and at its other end d4 to the spindle It. The valve 43 controls thesupply of pressure medium to, and the discharge of pressure medium from,thecylinder 4|. Since the valve 43 is connected to the spindle t6constituting the rod of the piston 40, the said valve will always berestored to its normal or central position shown, after a regulation hasbeen completed. The servo-motor 4| constitutes a yielding couplingbetween the fuel regulator 24 and the governor l I since the spindle I6is free to slide through a packing 45 in the piston 40. A spring 35bears at its upper end against the piston 40 and at its lower endagainst a spring plate 36 secured to the spindle 16. The spring 35 is ofsuch strength that when the piston 40 is moved downwardly within thecylinder 4!, the spindle I6, and therefore the valve H and fuelregulator are operated. The piston 4i) is biased by a spring 6t whichtends to move the piston 46 upwardly against the pressure medium withinthe cylinder ll above the piston In the event of the supply'of pressuremedium to the pipe l8 and therefore to the field-regulat ing servo-motor28 failing or becoming defective, the spring 36 moves the piston 49upwardly 50 as to engage the stop or collar 33, and thus tends to movethe bell-crank lever 22 into the position 0, the engine being thusstopped. When, on the other hand, pressure medium is available from thepipe i8 and the valve 43 is moved upwardly from the position shown, thismedium acts on the 'andmeans controlling the supply of fluid to thecylinder, a fuel regulator for the engine, means operatively connectingthe piston of the control piston 40 from above so that the spring 48 iscompressed and the piston 40 thus descends, the valve 43 returning tothe central position shown. The spring 46 cannot now return the piston40 in the upward direction by reason of the pressure medium enclosed inthe cylinder 4| above the piston 40. Further, should pressure mediumleak downwardly past the piston 40 or past the valve 43, the latter willautomatically be moved upwardly by the resulting upward movement of thepiston 40 and spindle I6. Further pressure medium will now be admittedto the cylinder 4| above the piston 40 which is thus restored to itsposition of equilibrium, i. e. clear of the stop 38.

If the engine I is stopped by operating the lever 3|, the spindle I6 isthus moved upwardly independently of the position of the governor H andindependently of the position of the piston 40. Thus, not only is thefuel supply to the engine cut off so as to stop the engine, but thevalve H is moved upwardly so that the rheostat arm 2| is moved into theposition shown dotted, that is to say corresponding to maximumexcitation of the generator 2. During the clockwise movement of thebell-crank lever 22, the lever 42 turns about the sleeve I3 as pivot andthe valve 43 is moved upwardly. The fact that the piston 40 is thenforced downwardly does not affect the position of the rod l6, fuelregulator 24 and valve H. A stop 41 within the cylinder 4| prevents thepiston 40 from moving down sufficiently far within the cylinder to cutoff the supply of pressure medium to the cylinder 4| beneath the piston40.

When the engine has been brought to rest, the supply of pressure mediummay also cease. This will not, however, affect the servo-motors 20 and4| so that the resistance 1 will remain cut out of the circuit and, whenthe engine is restarted and the switch 48 closed, the maximum excitationcurrent supplied from the auxiliary generator 3 will be immediatelyavailable.

It will be understood that the constructions described above are givenby way of example only and that details may be modified.

I claim:

1. In an internal combustion engine-electric power unit, the combinationwith a field-regulating servo-motor, of valve means for controlling thesupply of power to the servo-motor, a governor driven by the engine, afuel regulator for the engine, interconnecting means through which thegovernor controls both the said control valve and the fuel regulator,said governor being yieldingly coupled to the interconnecting means sothat the fuel regulator can be adjusted to reduce or cut off the fuelsupply, independently of the governor, an automatic control devicenormally held inoperative by power derived from the source whichsupplies the servo-motor, and means whereby in the event of the saidpower supply becoming defective the automatic control device actsthrough the interconnecting mechanism on the fuel regulator so as toreduce or cut off the fuel supply to the engine.

2. In an internal combustion engine-electric power unit having agenerator driven by the engine, the combination which comprises a fieldregulator for the generator, a field-regulating servo-motor operativelyconnected to the field regulator, a source of fluid under pressure foroperating the servo-motor, an automatic control device comprising acylinder, a piston in the cylinder biased by a spring, means connectingthe cylinder to the source of fluid under pressure,

device with the control valve of the servo-motor,

separate means operatively connecting the piston of the control devicewith the fuel regulator, whereby movement of the piston in one directionagainst the action of the biasing spring transmits movement to the fuelregulator and to the valve of the servo-motor increasing the fuel supplyand decreasing the excitation, and movement of the piston in the otherdirection causes the fuel regulator to decrease the fuel supplied to theengine and the servo-motor to increase the excitation.

3. In an internal combustion engine-electric power unit, the combinationwith a field-regulating servo-motor, of an automatic control device'normally held inoperative by power derived from the source whichsupplies the power for actuating the servo-motor, interconnecting meansbetween the automatic control device and a fuel regulator for theengine, so that in the event of the said power supply becoming defectivethe automatic control device operates the fuel regulator to reduce orcut off the fuel supply, means for controlling the fuel supply to theengine at will comprising a stop member which is operable to cause thefuel regulator to reduce or cut off the supply of fuel to the engine,and means for setting the field-regulating servomotor for maximumexcitation of the main generator when the stop member cuts off the fuelsupply.

4. A power unit which comprises in combination, an internal combustionengine, an electrical generator driven by the engine, field-excitingmeans for said generator, 2. servo-motor operatively connected to thefield-exciting means, a fuel regulator for said engine, means responsiveto the engine speed for controlling the fuel regulator, an automaticcontrol device for imposing an additional control on the fuel regulator,manual means for operating the'fuel regulator connected to theservo-motor, whereby the field. excitation may be varied simultaneouslywith variations in the fuel regulator and means operativelyinterconnecting the servo-motor, the means responsive to engine speedand the automatic control device, whereby an interruption or defect inthe servo-motor action may cause the fuel to be cut off, and operatingthe fuel regulator by said manual means may cause the field.- excitationto be set at a maximum.

5. In an internal combustion engine-electric power unit, the combinationwith a field-regulating servo-motor, of an automatic control devicenormally held inoperative by power derived from the source whichsupplies the power for actuating the servo-motor, interconnecting meansbetween the automatic control device and a fuel regulator for theengine, so that in the event of the said power supply becoming defectivethe automatic control device operates the fuel regulator to reduce orcut off the fuel supply, means for controlling the fuel supply to theengine at will comprising a stop member which is operable by suitableremote control means to cause the fuel regulator to reduce or cut offthe supply of fuel to the engine, and means for setting thefield-regulating servo-motor for maximum excitation of the maingenerator when the stop member cuts off the fuel supply.

6. In an internal combustion engine-electric power unit, the combinationwith a field-regulating servo-motor, of an automatic control devicenormally held inoperative by power derived from the source whichsupplies the power for actuating the servo-motor, interconnecting meansbetween the automatic control device and a fuel regulator for theengine, so that in the event of the said power supply becoming defectivethe automatic control device operates the fuel regulator to reduce orcut off the fuel supply, means for controlling the fuel supply to theengine at will comprising a stop member which is operatively connectedto the field-regulating servomotor to cause the fuel regulator to reduceor out off the supply of fuel to the engine, and means for setting thefield-regulating servomotor for maximum excitation of the main generatorwhen the stop member cuts 01f the fuel supply.

7. The combination with an internal combustion engine driving anelectric generator which comprises a field regulator for the generator,a servo-motor arranged to operate the field regulator, a governor drivenby the engine, a fuel regulator for the engine, a valve controlled meansoperatively connected to the servo-motor, a rodsystem connecting thevalve controlled means to the fuel regulator and to the governor, amanually operated device for shutting 01f the supply of fuel to theengine, a yieldable coupling in the rod-system, said rod-system beingoperable both by means of the speed governor and the manual controlmeans through the yieldable coupling.

ADOLF BRUNNER.

